•I
w
S iz e . C e lls ’t l - ’l l mm. diam. ; zygospores ‘1 mm. diam.
Narrow diameter *08 mm.
P e tit Spirogyra p. 31, t. 12, f. 1, 2. Kutz. Tab. v. t. 27, f.
3. Kirsch. Alg. Schl. p. 118. Rabh. Alg. Eur. iii. 245.
Zygtiema orhiculare, Hass. Alg. p. 138, t. 19. Jenner FI.
Tunb. Wells 178.
Zygnema alternatum, Hass. Alg. 139, t. 20.
Zygnema interruptum, Hass. Alg. 140, t . 21. Ann. Nat.
Hist. 1843, p. 432.
Zygnema maximum, Hass. Ann. Nat. Hist. x. (1842), p. 36.
Spirogyra alternata, Kutz. Spec. 442. Rabh. Alg. iii. 248.
Spirogtjra aetijor-mis, Kutz. Tab. v. t. 28, fig. 1 (not P e tit).
Rabh. Alg. iii. 246. Cleve Mon. Zyg. p. 15 (in part).
In ponds, &c. Fruiting in autumn.
There is nothing inconsistent in Cleve’s suggestion that Hassall’s
three plates 19, 20, and 21 all belong to the same species. No reliance
can be placed on the width of the chlorophyll bands, nor the little
difference in the breadth of the cells. Of course the disturbance in the
bands of the conjugated cells is due to the conjugation. When this
species is really in fruit there can be no difficulty in its determination,
and, without fruit, it is folly to waste time in attempting to guess at the
relationship of any species.
Hassall says that “ it is fonnd in ponds and dykes whose waters are
deep and permanent, and it does not conjugate until near the end of
summer.” “ Cells when in a state of conjugation, a little longer than
broad, prior to which, however, they are frequently not half so long as
broad ; winding round the interior of these are about eight spiral
threads, the granules in them being small.”
Plate XXXIV. fig. 1. a, sterile cells X 200; b, conjugating cells with
zygospores X 200 ; c, outline of zygospore X 400.
Spiio g y ra b e llis . Hassall.
Sterile cells with the ends truncate, and usually 14 times
(rarely 3 times) as long as broad ; chlorophyll bands 5 to 6,
making to 1 tnrn, or nearly erect.
Spores orbicular, depressed, with the membrane punctate or
porose, chestnut colour.
Sporiferous cells persistent, swollen.
Germinating plant cylindrical, radical cell short and sub-
cylindrical.
S i z e . C e l ls -0 7 - - 0 8 m m . ; z y g o s p o r e - 0 7 - '0 8 m m . d iam .,
• 0 5 - ’0 6 m m . th i c k .
Cleve Monogr. Zygn. p. 18, t. 8, f. 2 to 5. P e tit Spir. p.
31, t. 10, f. 1 to 3.
Zygnema bella, Hass. Alg. p. 142, t. 24. Ann. Nat. Hist.
X. (1842), p. 37. Jenner FI. Tunb. Wells 178.
Spirogyra subcequa, Kutz. Tab. Phy. v. t. 26, f. 2.
Rhynchonema rostratum, Kutz. Tab. Phy. v. t. 34, f. 3. (Not
Zygnema rostratum, Hass. Alg. t. 33, f. 1.)
Zygnema neglectum, Hass. Alg. t. 23, f. 1 (not Petit). Hass.
Ann. Nat. Hist. x. 37. Jenner FI. Tunb. Wells 178.
In ponds. Fru itin g in August.
This species is rather a characteristic one, of which it appears to us
that Zygnema neglectum, Hass., is only a form with three chlorophyll
bands. If the two species of Hassall are drawn to the same scale, it is
difficult to indicate any specific difeerence. The Rhynchonema rostratum
ot Kutzing IS referred by Cleve to this species, bnt the Zygnema
rostratum ot Hassall appears to be different, with thicker filaments and
much longer zygospores, and is rather referable to Bpirogyra nitida.
The Spirogyra Jieglecta of Petit cannot be the Zygnema neglectum of
Hassall.
^ This species is thus described by H a s s a l l “ Filaments about a foot
in length, with truncate extremities j of considerable though rather less
diameter than those of S, nitida, mucous, glossy, and of a deep and
beautiful green colour j investing membraue of the cells very evident
and transparent. Cells in the yonng filaments scarcely so long as broad,
but their length exceeds their breadth in those which have conjugated ;
round the interior of the cells five or six loose spiral tubes may be
laintly discerned.; these contain the reproductive globules {sic), which
are large and distinct, with a dark central nucleus. Sporangia oval
sometimes almost circular and flattened, lying in inflated cells, the
cavity of which they do not fill.”
Plate XXXIV. Jig. 2. a, sterile cells X 200; b, conjugating cells with
zygospores x 200; c, fertile cells of Rhynchonema form with zygospore
X 200 ; d, outline of zygospore x 400.
B. Chlorophyll bands single or double (rarely ternate).
Spirogyra p o r tic a lis . Vauch.
Sterile cells with the extremities truncate, 2 to 4 times
longer than the diameter ; chlorophyll bands single, or binate
rarely ternate. ’
Spores obtuse, ovoid, 14 times longer than the diameter,
membrane even, chestnut colour.
Sporiferous cells equal to the length of the spore, or twice as
long, more or less turgid.
Siz e . Cells ■032-’05 mm. diam. Zygospore *08 X •048-’05
mm.
Cleve Monog. Zygn. p. 22, t. 5, f. 8 to 13.
Conjugata porticalis, Vauoh. Conf. p. 66, t. 5, f. 1 .
In ditches, &c. Fru itin g in spring.
var. a. q u in in a .
Chlorophyll bands usually single.
S iz e . Cells -035-'045 mm., about twice as lono-
Zygnema quininum, Hass. Alg. t. 28, f. 1, 2. Harv. Man p
143. Landsborough Brit. Seaweeds p. 362. Eng. FI. v 362
Harv. Man. 143. Johnst. FI. Berw!
TT Hib. 231. FI. Devon
11. 50. Hook. FI. Scot. ii. 80. Dickie Bot. Guide, 296.
f